The invention relates to the field of recording and reproducing real-time digital information such as digital audio and video information.
The invention relates to a method and apparatus for simultaneously recording and reproducing a real time information signal, such as a digital video signal, on a disc like record carrier. The record carrier may be of the magnetic or the optical type. An apparatus for recording a real time information signal, such as an MPEG encoded video information signal, on a record carrier is known from U.S. Pat. No. 5,579,183 (PHN 14818). The record carrier in the said document is in longitudinal form.
Disc like record carriers have the advantage of a short access time. This enables the possibility of carrying out xe2x80x98simultaneousxe2x80x99 recording and reproduction of information signals on/from the record carrier. During recording and reproduction, information should be recorded on/reproduced from the record carrier such that an real time information signal can be recorded on the record carrier and xe2x80x98at the same timexe2x80x99 a real time information signal recorded earlier on the record carrier can be reproduced without any interruption. For such a simultaneously recording and reproducing, it is required to interleave read and write actions such that record and playback channels can guarantee sustained performance at a peak data rate without buffer overflow or underflow. The R/W cycling time should be as short as possible. Short cycle times imply smaller buffer sizes for the read and write buffer and imply shorter response times to user actions.
On a disc like record carrier real-time data may be allocated contiguously within fixed sized fragments while a fragment area may have an arbitrary location on a disc. For a maximum data rate preferably data in a fragment should be written and read in one write action and one read action respectively. This results in a minimum number of jumps of reading or writing means to a new location and therefore to a maximum performance in data rate. This can be referred to as 2-jump scheduling.
However, only a single read and single write action within a R/W cycle is not suitable for seamless reproducing or playback of edited files. With edited playback files, a playback sequence is defined to be a sequence of blocks or portion of blocks of information written in a fragment area. The latter occurs usually around the transition from some part of an original recording to the next part of the same or another recording, as a result of editing. One read action in a R/W cycle may result in reading only a portion of a block of information in a fragment. And this may result in an underflow of a corresponding read buffer.
This disadvantage is avoided with the proposed read/write-scheduling scheme.
The above citations are hereby incorporated in whole by reference.
The invention aims at providing measures to enable the various requirements, such as the ones described above. In accordance with the invention, the method for simultaneously recording and reproducing real time information signals, such as digital video signals, on/from a disc like record carrier having a data recording portion which is subdivided into fixed sized fragment areas, include:
receiving a first information signal for recording;
processing the first information signal into a channel signal for recording on the disc like record carrier wherein the processing includes converting the first information signal into blocks of information of the channel signal, and wherein the processing is further adapted to convert the first information signal into blocks of information of the channel signal, such that the size of blocks of information can be variable and satisfy the following relationship:
SFA/2xe2x89xa6size of a block of the channel signalxe2x89xa6SFA where SFA equals the fixed size of a block of the fragment area;
writing the channel signal on the disc like record carrier wherein the writing includes writing a block of information of the channel signal in a fragment area on the record carrier;
reading blocks of information of the channel signal from fragment areas of the record carrier;
processing the blocks of information of the channel signal for obtaining a second information signal;
carrying out the simultaneous recording and reproducing in subsequent cycles, a cycle includes:
no more then one write action for contiguously writing a block of information of the channel signal into a fragment area on the record carrier and
one or more read actions for contiguously reading each action at least a portion of the block of information of the channel signal from the record carrier.
Further, the apparatus for simultaneously recording and reproducing real time information signals, such as digital video signals, on/from a disc like record carrier having a data recording portion which is subdivided into fixed sized fragment areas, includes:
input apparatus for receiving a first information signal for recording;
first signal processing means for processing the first information signal into a channel signal for recording on the disc like record carrier;
writing apparatus for writing the channel signal on the record carrier;
the first signal processing means being adapted to convert the first information signal into blocks of information of the channel signal, the writing means being adapted to write a block of information of the channel signal in a fragment area on the record carrier, and
wherein the processing is further adapted to convert the first information signal into blocks of information of the channel signal, such that the size of blocks of information can be variable and satisfy the following relationship:
SFA/2xe2x89xa6size of a block of the channel signalxe2x89xa6SFA where SFA equals the fixed size of a block of the fragment area;
the apparatus further includes:
reading apparatus for reading blocks of information of the channel signal from fragment areas on the record carrier;
second signal processing apparatus for processing the blocks of information of the channel signal so as to obtain a second information signal;
output apparatus for supplying the second information signal reproduced for the record carrier,
the simultaneous reading and writing of the first and second information signals respectively being carried out in subsequent cycles, a cycle including:
no more then one write action for contiguously writing a block of information of the channel signal into a fragment area on the record carrier and
one or more read actions for contiguously reading each action at least a portion of the block of information of the channel signal from the record carrier.
Initially a record carrier may be obtained by writing an amount of information, which equals the fragment area size. This results in a maximal efficiency with respect to memory allocation during initial writing of a record carrier. This will be referred to as a full-fragment (FF) condition. With subsequent simultaneous recording and writing, writing of a contiguous amount of information is allowed which equals at least half the fragment size. This will be referred to as a half-fragment (HF) condition. By allowing more than one read action in a R/W cycle, a seamless playback of edited files can now be guaranteed during simultaneously recording while maintaining a high data rate. Since portions of the block of information to be read are no smaller, no more than two additional jumps are needed to read an amount of at least the fragment size.
An advantageous embodiment is characterized by executing maximal three read actions in one cycle. A worst-case R/W cycle has a total of 4 jumps with three read actions for reading respectively a last, a complete and a first portion of a block of information in a fragment. This will be referred to as 4 jump scheduling.
Further advantageous embodiments with the above mentioned full-fragment (FF) condition and half-fragment (HF) condition, are characterized by varying the cycle time. As will be explained hereafter in detail, a maximum of only two read actions in a cycle is obtained resulting in a 3-jump scheduling. Thus reducing the total number of jumps in a cycle and increasing the net data rate or lower the performance requirements.
A first embodiment employing a variable cycle time is obtained by delaying a subsequent write action if a predetermined condition for a read action is not met. By postponing a subsequent write action, in specific cases, reading of a complete portion of a block of information in a fragment can be finished.
Again, in general, without imposing restrictions upon the minimal amount read or written in a cycle, advantageous embodiments employing a varying cycle time are characterized by executing maximal two read actions in one cycle.
A next advantageous embodiment is characterized by ordering the reading of the portions of the bock of information in the cycles such that a total jump time for localizing the fragments in a cycle is minimal.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments hereafter in the figure description, in which